This invention relates to a coating and lubricating finish for surgical devices, preferably for multifilament biosorbable sutures.
It is known that suture materials are often coated with various substances to improve their handling characteristics, e.g. the U.S. Pat. Nos. 4,532,929; 4,201,216; 4,185,637; and 4,027,646 teach the use of a composition comprising a fatty acid salt or ester as a suture coating. Also, U.S. Pat. No. 4,047,533 describes the use of a water soluble poly(alkylene oxide) as a coatings for a multi-filament bioabsorbable suture. A survey included in U.S. Pat. No. 4,047,533 outlines several other approaches which are useful in improving suture knot trying performance. All of these patents are incorporated herein by reference. In summary, there is a constant research effort in the coating field to improve suture handling characteristics.
It has been discovered that a commercially available bio-polymer is useful as a suture coating. The bio-polymer can be obtained from ICI, Ltd., U.K. or from Poly-sciences Inc., Warrington, PA. For a description of the polymer, see published European patent applications Nos. 104,731; 91,224; and 69,497; and U.K. Pat. No. 2,120,671, all of which are incorporated herein by reference.
The polymer can consist of a homopolymer of hydroxy butyrate linkages, or a copolymer having approximately 70 or 80% hydroxy butyrate linkages and the remainder hydroxy valerate linkages. The homo- and copolymer can be manufactured by a bio-mass fermentation process.
The coating formulation uses methylene chloride as a solvent.
An object of this invention is to provide bioabsorbable, water insoluble coatings for multifilament sutures or bioimplantable devices. The preferred coating systems may be applied to any suture material where it is desired to improve fiber lubricity, suture knot run-down characteristics and the like. The coating is particularly useful with synthetic absorbable multifilament sutures composed of polyactide, polyglycolide, copolymers of lactide and glycolide, copolymers of glycolide and trimethylene carbonate, poly(p-dioxanone), poly(alkylene oxalate), and copolymers of glycolide and alkylene oxides, etc. Poly(.beta.-hydroxybutyrate)s are bioabsorbable materials.
The coating composition could be poly(.beta.-hydroxy-butyrate) or polymers and copolymers represented by the following general structural units: ##STR2## wherein each R.sub.1 is a lower alkyl group, preferably methyl. U.S. Pat. No. 4,372,311 (Potts) teaches the use of poly(.beta.-hydroxybutyrate) as a coating material for water soluble disposable articles. However, the potential of using poly(.beta.-hydroxybutyrate) and its copolymers as coatings for bioabsorbable surgical devices was not disclosed. In this invention, the poly(.beta.-hydroxybutyrate) and its copolymers are specifically used to coat water insoluble surgical sutures and devices to improve their handling characteristics and biocompatability.
A bioabsorbable coating for a surgical device has been invented. The coating comprises a copolymer having about 60 to 80 weight percent of .beta.-hydroxybutyrate linkages. In one embodiment the inherent viscosity of the copolymer measured at 30.degree. C. on a 0.5 percent weight per volume solution of the copolymer in hexafluoroacetone sesquihydrate is about 1.5 to 5.0. In a specific embodiment, the inherent viscosity is up to about 4.0.
A coating for a bioabsorbable suture has been invented. The coating comprises a bioabsorbable copolymer having about 60 to 80 weight percent of .beta.-hydroxybutyrate linkages and the remaining linkages comprising at least .beta.-hydroxyvalerate. In one embodiment, the inherent viscosity of the copolymer measured at 300.degree. C. on an 0.5 percent weight per volume solution of the copolymer in hexafluoroacetone sesquihydrate is about 1.5 to 4.0. In another embodiment, the in vivo absorption time is about one year.
Finally, a coating for a synthetic bioabsorbable suture has been inserted. The coating comprises a bioabsorbable copolymer having up to about 60 to 80 weight percent of .beta.-hydroxybutyrate linkages and the remaining linkages comprising .beta.-hydroxyvalerate. The copolymer has an inherent viscosity of about 1.5 to 5.0 measured at 30.degree. C. on a 0.5 percent weight per volume solution of the copolymer in hexafluoroacetone sesquihydrate. The coating further comprises the copolymer in combination with a stearoyl lactylate having the formula: ##STR3## wherein X is at least two, and R is an alkaline-earth metal. In a specific embodiment, X is two and R is calcium